[Document Type] Specificatio~i
[Title of the Invention] STEEL SHEET USED TO MANUFACTUREA
CONTAINER AND METHOD OF MANUFACTURING THE SAME
[Technical Field of the Invention]
[OOOl]
The present invention relates to a steel sheet used to nlanufacture a container
and a method of manufacturing the same, and particularly to a steel sheet used to
nlanufacture a container that is used to manufacture 2-piece cans and 3-piece cans and
is excellent in tenns of corrosion resistance, adhesion and weldability, and a method of
~nanufacturingth e same.
Priority is claimed on Japauese Patent ApplicationNo. 2012-228196, filed on
October 15,2012, and the contents of which are incorporated herein by reference.
[Related Art]
[0002]
As steel containers mainly used in the beverage can field, there are 2-piece
cans and 3-piece cans.
The 2-piece can refers to a can body in which a can bottom and a can
cylindrical portion are integrated together, and DrD can, DI can and the like are known.
The 2-piece can is fornied and manufactured through drawing, ironing, bending aud
unbending or a combination of the above-described processes. Tin steel sheet (Sn
plating steel sheet) or tin-free steel (TFS, electrolytically chron~ateds teel sheet) are
steel sheets used to inanufacture the can bodies of 2-piece cans, and are selectively
used depending on usages or processing tnetl~ods.
[0003]
Meanwhile, the 3-piece can refers to a can body in which a can cylindrical
portion and a can bottom are separated from each other, and the can cylindrical
portions are mainly manufactured by forming a thin steel sheet into a cylindrical shape
and joining joints through welding. Cans having a can cylindrical portion
manufactured through welding as described above are called welded cans. In
addition, lightly tin coated steel sheets or Ni plating steel sheets are used as materials
to manufacture the can cylindrical portior~so f 3-piece cans. In addition, TFS and
other materials are used as materials used to manufacture the can bottoms of 3-piece
calls.
[0004]
In both 2-piece cans and 3-piece cans, the can outer surface is printed to
appeal the values (commercial values) of contents in the cans to consumers. In
addition, the can inner surface is coated with a resin to ensure corrosion resistance.
For conventional 2-piece cans, after forming can bodies, the can inner
surfaces were coated through spraying or the like, and curved surface printing was
performed on the can outer surfaces. In recent years, laminate 2-piece cans obtained
by forming a steel sheet on xvllich a PET film has additionally been laminated in
advance into cans have emerged (Patent Documents 1 and 2).
In addition, 3-piece welded cans as well, bodies of which were manufactured
by welding a cot~ventionaslt eel sheet having a coated can inner surface and a printed
can outer surface, 3-piece cans manufactured using a laminate steel sheet on wv11ich a
previously-printed PET film has been stacked instead of being coated and printed have
also emerged (Patent Documents 3 and 4).
[OOOS]
When manufacturing a 2-piece can, drawing, ironing, and bending and
unbending are performed on a steel sheet used to manufacture a container. In
addition, when manufach~ringa 3-piece can, neck processing or flange processing is
performed on a steel sheet used to manufacture containers, and, sometimes, expansion
of a steel sheet used to manufacture containers is performed to improve designability.
Therefore, to laminate steel sheets used as steel sheets used to manufacture containers,
there is an increasing demand for excellent film adhesion that can withhold the abovedescribed
processes.
[0006]
In a case in which a Sn plating steel sheet is used as a steel sheet used to
manwfacture a container, due to the excellent sacrificial protection action of Sn, the Sn
plating steel sheet exhibits excellent corrosion resistance against acidic contents in
cans. However, since a brittle Sn oxide is present on the olrtermost layer of the Sn
plate, the adhesion of a film formed on the plate is unstable. Therefore, when the Sn
plating steel sheet is subjected to the above-described drawing and other processing
there are problerns in that the film is exfoliated, and, furthermore, corrosion begins to
occur at places in xvhich the adhesion between the film and the steel sheet used to
manufacture containers is uot sufficient.
[0007]
Thus, Ni plating steel sheets are being used as laminate steel sheets used to
manufacture containers that are excellent in terms of workability and adhesion, and,
furthennore, are weldable (Patent Document 5).
Regarding Ni plating steel sheets, a variety of techniques have been thus far
disclosed (for example, Patent Document 9). In addition, ~vhileth ere areNi plating
steel sheets having a dull surface like Sn plating steel sheets, Ni plating steel sheets on
which bright plating is perfomled using a brightening agent-added Ni plating method
are also known (Patent Documents 6 and 7).
[OOOS]
However, unlike Sn, Ni does not have a sacrificial protection action in acidic
solutions. Thus, it is known that, in a case in which the Ni plating steel sheet is used
to manufacture containers that contain highly corrosive contents such as an acidic
beverage, piercing corrosion in which corrosion proceeds from defects such as pin
holes in a Ni plating layer in the film thickness direction occurs, and the Ni plating
steel sheet is pierced within a short period of time. Therefore, there has been a
demand to improve the corrosion resistance of the Ni plating steel sheets.
Regarding the above-described problem, to reduce piercing corrosion, a Ni
plating steel sheet in which the steel component of a tin mill black plate (base steel
sheet) is adjusted so that the electrical potential of a steel sheet to be plated
approximates in the positive direction has been disclosed (Patent Document 8).
[0009]
In addition, it is known that, wvl~en manufacturing Ni plating steel sheets, Ni in
the Ni plating layer is oxidized due to dissolved oxygen in a plating bath or oxygen in
an atmosphere such that a Ni oxide film is formed on the surface of the Ni plating layer.
However, in a case in which a chromate treatment is performed on the Ni plating layer
for the purpose of the improvement of corrosion resistance, the amount of chromate
precipitation varies depending on the film-forming state of the above-described Ni
oxide film, and there is a problem in that the poor appearance of containers is caused.
Regarding the above-described problem, a method of ensuring favorable
appearances by perfor~ningN i plating, and then forming a uniformNi oxide film on
the Ni plating layer through a controlled thermal treatment has been disclosed (Patent
Document 10).
[Prior Art Document]
[Patent Document]
[OOl 01
[Patent Document I] Japanese Unexamined Patent Application, First
Publication No. 2000-263696
[Patent Document 2] Japanese Unexamined Patent Application, First
Publication No. 2000-334886
[Patent Document 31 Japanese Patent No. 3060073
[Patent Docutllent 41 Japanese Patent No. 2998043
[Patent Document 51 Japanese Unexamined Patent Application, First
Publication No. 2007-23 1394
[Patent Docu~r~e6n1t Japanese Unexatnined Patent Application, First
Publication No. 2000-26992
[Patent Document 71 Japanese Unexamined Patent Application, First
Publication No. 2005-149735
[Patent Document 81 Japanese Unexamined Patent Application, First
PublicationNo. S60-145380
[Patent Document 91 Japanese Unexamined Patent Application, First
Publication No. S56-169788
[Patent Document 101 Japanese Unexamined Patent Application, First
Publication No. H10-265966
[Disclosure of the Invention]
[Problems to be Solved by the Invention]
[OOll]
In the invention described in Patent Document 8, although there was a certain
degree of effect in reducing piercing corrosion, the effect was insufficient with the
simple adjustment of the steel con~ponenot f the tin mill black plate, and there was a
demand for additional ilnprovement of corrosion resistance. In addition, in the
invention described in Patent Document 8, since the steel component of the tin mill
black plate was limited, the Ni plating steel sheet was applicable only to some usages.
Therefore, there was a demand for Ni plating steel sheets applicable to diverse contents
or diverse can shapes.
[0012]
In addition, while the invention described in Patent Document 10 could ensure
favorable appearances, no consideration was given to the piercing corrosion of the Ni
plating layer, and thus the corrosion resistance of the plating steel sheet was
insufficient.
[0013]
Therefore, the invention has been made in consideration of tlie abovedescribed
problems, and an object of the invention is to provide a steel sheet used to
manufacture a container which is excellent in terms of corrosion resistance, adhesion
and wveldability, and a method of tnanufacturing the same.
[Means used to Solve the Problem]
[0014]
As a result of studies to achieve the reduction of piercing corrosion, the
present inventors found that, when one or more of a liydroxyl Ni and a Ni oxide is
included not on a surface of a Ni platiug layer but inside the Ni plating layer, the
corrosion resistance with respect to piercing corrosion can be iulproved. Specifically,
when a Ni plating layer including one or more of a Iiydroxyl Ni arid a Ni oxide was
formed on a steel sheet, that is, a tin mill black plate, a phenomenon in which the
piercing corrosion rate was decreased when corrosion proceeded from defects such as
pin holes in the Ni plating layer was observed (refer to FIG. I. FIG. 1 will be
described below in detail).
[0015]
The above-described phenomenon is assumed to proceed with the following
mechanism.
The hydroxyl Ni and the Ni oxide are easily dissolved in acidic solutions.
That is, since the hydroxyl Ni and the Ni oxide in the Ni plating layer are preferentially
dissolved in the initial phase of corrosion, it is considered that an increasing number of
voids are included inside the Ni plating layer as the corrosion proceeds. In addition,
since the number of voids appear in the Ni plating layer, it is considered that corrosion
(piercing corrosion), which concentrated at pin holes if the conventional steel sheet is
used, is dispersed to the voids, the corrosion type changes from piercing corrosion to
general corrosion or corrosion (interfacial corrosion) at the interface between the Ni
plating layer and base iron, and the rate of the proceeding piercing corrosion decreases.
Furthermore, as a result of additional studies based on the above-described
knowledge, it was found that, ~vlleno ne or more of the hydroxyl Ni and theNi oxide
was dispersed and distributed in the thickness direction of the Ni plating layer, piercing
corrosion could be fi~rtbere duced.
The inventors invented a steel sheet used to manufacture a container that was
excellent in terms of corrosion resistance, adhesion and weldability using the abovedescribed
phenomenon.
[0016]
That is, the invention obtained from the above-described knowledge is what
will be described below.
(1) According to an aspect of the invention, there is provided a steel sheet
used to ma~lufacturea container including aNi plating layer; and a chromate film layer
or a film layer including Zr, on theNi plating layer, in \vI~iclich the Ni plating layer
includes one or more of a hydroxyl Ni and a Ni oxide, the adhesion amount of the Ni
plating layer in terms of an amount of Ni is 0.3 g/n~o2r more, the concentration of
oxygen atoms of the Ni plating layer due to the hydroxyl Ni and the Ni oxide is I to 10
atomic%, an adhesion amount of the chromate film layer in terms of the amount of Cr
is 1 to 40 mg/m2, and the adhesion amount of the film layer including Zr in tenns of
the amount of Zr is 1 to 40 mg/m2.
(2) In the steel sheet used to manufacture a container according to the abovedescribed
(I), the concentration of the oxygen atom is 1 to 10 atomic% in an entire
area of a thickness of the Ni plating layer excluding a natural oxide film formed on a
surface of the Ni plating layer.
[0017]
(3) According to another aspect of the invention, there is provided a method of
~nanufacturinga steel sheet used to nlanufacture a container according to the abovedescribed
(I), the method including: a step of for~ningth e Ni plating layer including
one or more of the hydroxyl Ni and the Ni oxide by dipping a base steel sheet in a
plating bath and then performing an cathode-electrolysis under a current density higher
than a critical current density of precipitation of Ni, in which the plating bath consists
of an aqueous solution in which one or more of a Ni sulfate and a Ni chloride is
dissolved; anda step of forming the chromate film layer of which the adhesion amount
in terms of the amount of Cr is 1 to 40 mg/m2 on the Ni plating layer or a step of
for~ningth e film layer including Zr of which the adhesion amount in terms of the
amount of Zr is 1 to 40 mg/mn2, on theNi plating layer.
[Effects of the Invention]
[0018]
According to the invention, one or more of the hydroxyl Ni and the Ni oxide
is included inside the Ni plating layer, and the chromate film layer or the film layer
including Zr is formed on the above-described Ni plating layer, whereby it is possible
to provide a steel sheet used to manufacture a container .rvhich is excellent in terms of
corrosion resistance with respect to piercing corrosion, and, furthermore, is excellent in
terms of adhesion wit11 laminated resin films and weldability.
[Brief Description of the Drawing]
[0019]
FIG. 1 is a graph illustrating a relationship between a concentration of an
oxygen atom in a Ni plating layer and piercing corrosion depth in Example 2 of the
invention.
FIG. 2 is a graph illustrating a relationship between a concentration of a nickel
atom and the concentration of the oxygen atom in theNi plating layer, and a sputtering
time of X-ray pliotoelectron spectroscopy (XPS) in Invention Example 1 of Example 1
of the invention.
[Embodiments of the Invention]
[0020]
The invention is a steel sheet including a cliromate film layer or a film layer
including Zr on the Ni plating layer, and the Ni plating layer includes one or more of a
l~ydroxyNl i and a Ni oxide. Meanwl~ile,i n the steel sheet used to manufacture a
container of the invention, the adhesion atnount of the Ni plating layer in tern~so f the
amount of Ni is 0.3 g/ln2 or lnore, and the concentration of oxygen atoms in the Ni
plating layer due to the hydroxyl Ni and the Ni oxide included in the Ni plating layer is
1 to 10 atomic%. In addition, the adhesion anlount of the chromate film layer formed
on the Ni plating layer in terms of the amount of Cr is 1 to 40 mg/m2, and the adhesion
amount of the film layer including Zr in terms of the amount of Zr is 1 to 40 mg/m2.
[0021]
Hereinafter, a steel sheet nsed to manufacture a container which is an
embodiment of the invention will be described in detail.
[0022]
Asteel sheet used to manufacture a container according to the present
embodiment has a Ni plating layer including one or more of a hydroxyl Ni and a Ni
oxide formed on a surface of the steel sheet, and the Ni plating layer has an adhesion
amount of Ni of 0.3 g/n12 or more and the concentration of oxygen atoms of the
hydroxyl Ni and the Ni oxide of 1 to 10 atomic%.
In addition, a chromate fihn layer or a film layer including Zr is provided on
the surface of theNi plating layer. The chromate fihn layer has an adhesion amount
in terms of the amount of Cr of 1 to 40 mg/m2, and is formed 011 the Ni plating layer.
In addition, in a case in which a film layer including Zr is formed instead of the
chromate film layer, the film layer including Zr is formed on the Ni plating layer at an
adhesion amount in terms of the amount of Zr of 1 to 40 mg/m2.
[0023]
The steel sheet used to manufacture a container in the present embodiment is
a tin mill black plate. Examples of the steel sheet include cold-rolled steel sheets
manufactured through an ordinary process of ~l~anufacturinslga bs and processes such
as hot rolling, pickling, cold rolling, annealing and temper rolling. Here, there is no
particular limitation in the components or characteristics of the steel sheet according to
the embodiment, and, for example, low-carbon steel other steel generally used to
manufacture a steel sheet used to manufacture a container can be used.
In the embodiment, a Ni plating layer including one or more of a hydroxyl Ni
and a Ni oxide is formed on the above mentioned steel sheet, which is the tin mill
black plate, in order to ensure corrosion resistance, adhesion and weldability.
Meanwhile, hereinafter, the tin tilill black plate (base steel sheet) according to
the embodinletit will also be referred to simply as "steel sheet".
[0024]

Ni is a metal that is excellent in tenns of adhesion and forge-weldability (a
characteristic to be joined at a temperature of the tnelting point or lower) with respect
to steel sheets and can exhibit favorable weldability, and, when the adhesion atnount 111
tertus of Ni is set to 0.3 g/m2 or more in performing Ni plating on steel sheets, practical
adhesion, weldability and forge-weldability begin to be exhibited. Therefore, it is
necessary to set the amount in terms of Ni to 0.3 g/tn2 or more in the Ni plating layer.
The amount in terms of Ni is preferably set to 0.4 g/n12 or more, and more preferably
set to 0.6 g/m2 or more.
Meanwhile, when the adhesion amount of a Ni plate is increased, adhesion or
weldability improves; however, when the amount in terms of Ni exceeds 3 g/m2, the
effect that improves adhesion and weldability is saturated, which is econonlically
disadvantageous. Therefore, the upper limit of the amount in terms of Ni is
preferably set to 3 g/m2, and rnore preferably set to 2.5 g/m2 or less.
[0025]
The Ni plating layer includes one or more of a hydroxyl Ni and a Ni oxide.
That is, tlieNi plating layer may include both a 11ydroxylNi and a Ni oxide, and may
include any one of a hydroxyl Ni and a Ni oxide. Meanwhile, there is a plurality of
chemical forms of the Ni oxide, and, in the embodiment, it is dificult to specify what
form of the Ni oxide is included; however, mainly, NiO or NizO, is included.
In addition, in the conventional steel sheet and the method of manufacturing
the same (particularly Patent Document lo), techniques to form the Ni oxide on the Ni
plating layer by oxidizing the surface of the Ni plating layer have been studied;
however, unlike the related art, in the embodiment, the Ni plating layer includes both a
hydroxyl Ni and a Ni oxide. That is, while a Ni oxide layer was fornled on the
surface of aNi plating layer, and, on the other hand, the tin ~nilbl lack plate side of the
Ni plating layer was a double layer structure in which a pnreNi layer was formed in
the past, the Ni plating layer according to the embodiment includes a hydroxyl Ni and
a Ni oxide in the entire area in the thickness direction.
[0026]
The concentration of oxygen atoms due to the l~ydroxyNl i andlor the Ni
oxide included in the Ni plating layer is set to 1 to 10 atomic%.
When the content rate of the hydroxyl Ni and/or the Ni oxide in the Ni plating
layer is too low, tlie above-described piercing corrosion-reducing effect is not
sufficiently exhibited. At a concentration of oxygen atoms due to the hydroxyl Ni
andlor the Ni oxide included in the Ni plating layer of 1 atomic% or more, the piercing
co~rosionra te begins to be suppressed, and it is possible to reduce piercing corrosion.
From the above-described viewpoint, the concentration of oxygen atoms due to the
hydroxyl Ni andlor the Ni oxide included in the Ni plating layer is set to 1 atomic% or
Inore, preferably set to 2 atomic% or more, and more preferably set to 3.5 atomic% or
more.
On the other hand, when the content rate of the hydroxyl Ni andlor the Ni
oxide in the Ni plating layer becomes excessive, the forge-weldability of Ni is
impaired, and, conseq~ie~ltltyh,e weldability deteriorates. Therefore, the
concentration of oxygen atoms due to the hydroxyl Ni and/or the Ni oxide in the Ni
plating layer needs to be set to 10 atomic% or less, preferably set to 8.5 atomic% or
less, and more preferably set to 8 atomic% or less.
[0027]
The concentration of oxygen atoms due to the hydroxyl Ni and/or the Ni
oxide in the Ni plating layer can be measured by measuring a specimen after Ni plating
on which a chromate film layer or a filnl layer including Zr described below is not
present using X-ray photoelectron spectroscopy (XPS).
In addition, the Ni plating layer according to the embodiment may include
unavoidable impurities in addition to the above-described hydroxyl Ni or Ni oxide as
long as the effect of the invention is not impaired.
[0028]
In addition, in the Ni plating layer according to the embodiment, the
concentration of oxygen atoms due to the hydroxyl Ni or the Ni oxide is preferably 1 to
10 atomic% in the entire area of the thickness of the Ni plating layer excluding a
natural oxide film formed on the surface of the Ni plating layer.
The steel sheet used to manufacture containers according to the embodiment
is obtained by performing Ni plating on the tin mill black plate, and then forming the
chromate film layer or the film layer including Zr described below; However,
between the step of perforti~ingN i plating and the step of fornling the chromate film
layer or the filnl layer including Zr, there is a case in which the Ni plating steel sheet is
exposed to the atmosphere, air in the atmosphere and the surface of the Ni plating layer
react with eacli other, and Ni in the surface of the Ni plating layer is oxidized, thereby
forming an natural oxide film. In the above-described case, the oxygen concentration
distribution in the Ni plating layer becomes high on the surface of the plating layer.
However, the important fact in the embodiment is that one or more of the hydroxyl Ni
and the Ni oxide is included in the entire area of the Ni plating layer irrespective of the
formation of the natural oxide film on the surface of the Ni plating layer.
Therefore, in the Ni plating layer according to the embodiment, the
concentration of the oxygen atom dne to the hydroxyl Ni andlor the Ni oxide is
preferably 1 to 10 atomic% in the entire area of the thickness of the Ni plating layer
excluding a Ni oxide layer (natural oxide film) formed on the surface of the Ni plating
layer. When one or more of the hydroxyl Ni and the Ni oxide is unifortnly dispersed
in the entire area the thickness of the Ni plating layer excluding the Ni oxide layer
(natural oxide film) on the surface of the Ni plating layer, piercing corrosion that
concentrates at pin holes in the Ni plating layer can be dispersed using voids generated
by the dissolution of the llydroxyl Ni and the Ni oxide, and it becomes possible to
reduce the piercing corrosion rate.
[0029]

Since a Cr metal or a hydrated Cr oxide that configures the chromate film
layer has excellent chemical stability, the corrosion resistance of the steel sheet used to
manufach~rea container improves in proportion to the adhesion amount of the
chromate film layer. In addition, since the hydrated Cr oxide exhibits excellent
adhesion even in a heated n~oisturea tmosphere by forming a strong chemical bond
with a fiinctional group of a resin film, the adhesion of the chromate film layer to the
resin film improves as the adhesion amount of the chromate film layer increases.
From the above-described viewpoint, 1 mg/n12 or more of the chromate film layer in
terms of the amount of the Cr metal is required to exhibit sufficient corrosion
resistance and sufficient adhesion for practical use. The content rate of the chromate
filtn layer in terms of the amount of the Cr metal is preferably set to 2.5 tng/m2 or more.
Meanwhile, while the effect that improves the corrosion resistance and the
adhesion enhances as the adhesion amount of the chromate film layer increases, since
the hydrated Cr oxide in the chrotnate film layer is an electrically insulating body,
when the adhesion amount of the chromate filnl layer increases, the electric resistance
of the steel sheet used to manufacture a container becomes extremely high, and the
weldability deteriorates. Specifically, when the adhesion amount of the chromate
film layer in terms of the amount of the Cr metal exceeds 40 mg/m2, the weldability
extren~elyd eteriorates. Therefore, the adhesion a~nounot f the chromate film layer in
terms of the amount of the Cr metal needs to be set to 40 mg/m2 or less, and preferably
set to 30 mng/m2 or less.
[0030]

In addition, the filtn layer including Zr may be formed on the Ni plating layer
instead of the above-described chromate film layer. The fill11 layer including Zr is a
film made of a Zr compound, such as a Zr oxide, Zr phosphate, hydroxyl Zr or Zr
fluoride, or a composite film thereof. When the film layer including Zr is formed in
an adhesion at~lounitn terms of the aniount of a Zr metal of 1 mg/m2 or more, si~nilarly
to the above-described chromate film layer, the drastic improvement of the adhesion or
corrosion resistance of the film layer including Zr with respect to the resin film is
observed. Therefore, the adhesion amount of the filtn layer including Zr in terms of
the amount of Zr is set to I mg/m2 or more, and preferably set to 2.5 mg/111~o r more.
On the other hand, when the adhesion atnount of the film layer including Zr in
terms of the amount of the Zr metal exceeds 40 lng/tn2, the weldability and the
appearance deteriorate. Particularly, since the film layer including Zr is an
electrically insulating body, when the adhesion amount of the film layer including Zr
increases, the electric resistance of the steel sheet used to manufacture a container
becomes extremely high, and the weldability deteriorates. Specifically, when the
adhesion amount of the film layer including Zr in terms of the amount of tlie Zr metal
exceeds 40 mg/m2, tlie weldability extremely deteriorates. Therefore, the adhesion
amount of the Zr film layer in terms of the amount of the Zr metal needs to be set to 1
to 40 mg/m2, and preferably set to 30 mg/m2 or less.
[003 11
Next, a method of manufachtring a steel sheet used to manufacture a container,
which is an embodiment of the invention, will be described.
The method of manufacturing a steel sheet used to manufacture a container
according to the present embodiment includes, firstly, a step of forming the Ni plating
layer including one or more of the hydroxyl Ni and the Ni oxide by dipping a tin mill
black plate (base steel sheet) in a plating bath and then performing an cathodeelectrolysis
under a current density higher than a critical current density of
precipitation of Ni, in which the plating bath consists of an aqueous solution in which
one or more of aNi sulfate and a Ni chloride is dissolved, and a step of forming the
chromate film layer of which the adhesion atnount in telms of the amount of Cr is 1 to
40 mg/m2 on the obtained Ni plating layer or a step of fonning the film layer including
Zr of which the adhesion amount in terms of the amount of Zr is 1 to 40 mg/m2 on the
obtained Ni plating layer.
[0032]
A method of forming the Ni plating layer including one or more of the
hydroxyl Ni and theNi oxide on a steel sheet will be described
First, a tin mill black plate is dipped in a plating bath consisting of an aqueous
solution in which one or more of a well-known Ni sulfate and a well-known Ni
chloride is dissolved, and then a cathode-electrolysis is performed under a current
density which is higher than the critical current density of the precipitation of Ni.
When the cathode-electrolysis is performed under a current density set to be higher
than the critical current density of the precipitation of Ni as described above, it is
possible to promote the generation of a hydroxyl nickel or a nickel oxide by an
increase in pH at the interface of the plating layer, and it is possible to obtain the Ni
plating layer including one or more of the hydroxyl Ni and theNi oxide.
Meanwhile, the concentrations of the Ni sulfate and the Ni chloride are not
particularly limited, but it is possible to set the concentration of the Ni sulfate to 5 to
30% and theNi chloride to 5 to 30%.
In addition, the pH of the plating bath is not particularly limited, but it is
possible to set the pH to 2 to 4 from the viewpoint of liquid stability.
[0033]
The critical current density in the invention refers to a current density at
which the adhesion efficiency of Ni begins to decrease wlien gradually increasing the
current density, and is known to be dependent on the concentration of a Ni ion, the pH,
tlie flow rate of a liquid and tlie bath temperature of the plating bath. That is, there is
a tendency of the critical current density increasing as the concentration of aNi ion, the
pH, the flow rate of a liquid and the bath temperature become high. Mean~vhilet,h e
adhesion efficie~~coyf Ni can be computed from the adhesion aniount of Ni and tlie
amount of electric conduction.
For example, Patent Docutnents 8 and 9 describe a wide range of the current
density of 3 to 300 ~fdrn'. In a case in wliicli the Ni plating layer including the
hydroxyl Ni or the Ni oxide is formed by the cathode-electrolysis under a high current
density, it is possible to obtain a current density that is higher than 300 Ndmz
depending on the conditions of the plating bath.
On the other hand, there is a tendency of the critical current density being
decreased by decreasing the concentration of a Ni ion or the pH. That is, depending
on the conditions of the plating bath, the critical current density is exceeded at a lower
current density of 10 .4/dmz, and it is possible to obtain the Ni plating layer including
the liydroxyl Ni or the Ni oxide.
That is, to form t11eNi plating layer including one or more of the hydroxyl Ni
or the Ni oxide, it is extremely important to set the current density during the cathodeelectrolysis
to be higher than the critical current density. In a case in wvhichNi plating
is performed under conditions in which the current density is lower than the critical
current density, the pH at the interface of the plating layer does not sufficiently
increases, and it becomes difficult to promote the generation of the liydroxyl Ni or the
Ni oxide. As a result, it is not possible to sufficiently ensure the l~ydroxyNl i or the
Ni oxide included in the Ni plating layer.
[0034]
In addition, to more easily and more stably form the Ni plating layer including
the hydroxyl Ni or the Ni oxide, it is possible to use a bath in which a boric acid or a
Ni cl~lorideth at suppresses an increase in the pH at the interface is not used. In a bath
in ~vllicha boric acid or a Ni chloride is not used, since the critical current density
decreases, it is possible to obtain the Ni plating layer including the hydroxyl Ni or the
Ni oxide at a relatively low current density.
[0035]
Meanwhile, in a case in which plating is performed using a plating bath
including a boric acid, since there is a tendency of the pH in the interface increasing,
compared with a case in wllich a plating bath not including a boric acid is used, it is
necessary to set the current density to be higher.
[0036]
Meanwhile, it is possible to appropriately select one of a Ni plating method in
which the plating bath includes a boric acid and a Ni plating method in which the
plating bath does not include a boric acid depending on the treatment time in a plating
treatment facility to ~vliichth e method is applied. In addition, since the current
density to be used is set to a value higher than the critical current density by 10% or
more and preferably more than 20%, it is possible to manufacture the above-described
Ni plating layer including one or more of the hydroxyl Ni and the Ni oxide in an
industrially stable rnanner by performing the cathode-electrolysis.
[0037]
Meanwhile, the adhesion amount of Ni, the adhesion amount of the chromate
fihn layer described below, and the adhesion amount of the film layer including Zr can
be easily measured using a well-known analyzer such as a fluorescent X-ray apparatus
or an X-ray photoelectron spectroscope.
[0038]
Next, the chromate film layer of wvhich the adhesion amount in terms of the
amount of Cr is 1 to 40 mg/n12 or the film layer including Zr of which the adhesion
amount in terms of the amount of Zr is 1 to 40 mg/tn2 is forn~edo n the Ni plating layer
obtained in the above-described manner.
[0039]
It is possible to improve the corrosion resistance, the adhesion with the resin
film, and, particularly, the secondary adhesion after processes by forming the chromate
fihn layer on the Ni plating layer. The chronlate film layer col~sistso fa hydrated Cr
oxide or a hydrated Cr oxide and a Cr metal, and is formed usit~ga chromate treatment.
[0040]
As a metliod of the chromate treatment, any method of a dipping treatment in
which an aqueous solution of a variety of sodium salts, potassium salts, ammonium
salts and the like of a Cr acid is used, a spray treatment, an electrolysis treatment and
the like may be performed. Among the above-described methods, particularly, a
method in which a cathode electrolysis treatment is performed in an aqueous solutiot~
in which a sulfuric acid ion, a fluoride ion (including a complex ion) or a mixture
thereof is added to a Cr acid as a plating aid is industrially excellent.
[0041]
As a method of forming the film layer including Zr, for example, a wellknown
method, such as a dipping treatmer~mt ethod or a cathode-electrolysis treatment
method of a steel sheet after the formation of the above-described Ni plating layer in
an acidic solutio~in~c luding a Zr fluoride, a Zr phosphate and a fluoric acid as a main
component, may be employed.
[0042]
According to the above-described manufacturing method, it is possible to
~nanufactureth e steel sheet used to manufacture a container according to the
embodiment. Meanwhile, conditions other than the conditions of the above-described
manufacturing method may be appropriately determined in consideration of a plating
facility to be used and the like as long as the effects of the invention are not impaired.
[0043]
According to the embodiment, it is possible to improve the piercing corrosion
resistance of the steel sheet used to manufacture a container, and to improve
weldability, adhesion wit11 respect to the resin film, and adhesion with respect to the
resin film after processes.
[Examples]
[0044]
Next, the invention will be described in more detail using examples, but the
conditions in the present examples are employed to confirnl the feasibility and effect of
the invention, and the invention is not limited to the conditions described herein.
The invention can employ a variety of conditions or cornbinations of
conditions within the scope of the purpose of the invention as long as the object of the
invention is achieved.
[0045]
[Example 11
First, the examples and comparative examples of the invention will be
described, and the results are described in Table 1.
In the examples, specimens were produced using a method described in the
following (I), and performance evaluation was performed on the respective items (A)
to (D) in (2).
[0046]
(1) Method of producing specimens
[Steel sheet (tin mill black plate)]
A 0.2 mm-thick cold-rolled steel sheet for a tin plate with a temper grade of 3
(T-3) was used as a tin mill black plate.
[0047]
mi plating condition 11
Anickel sulfate having a concentration of 20%, a nickel chloride having a
concentration of lo%, and an aqueous solution having an adjusted pH of 2 and a
temperature of 35°C were used, and a cathode-electrolysis was performed under a
current density of 25 A/dm2 that exceeded the critical current density, thereby forming
a Ni plating layer on the steel sheet. The adhesion amount of Ni was controlled using
the electrolysis time.
[0048]
[Ni plating condition 21
A boric acid having a concentration of 3%, a nickel sulfate having a
concentration of lo%, a nickel chloride having a concentration of lo%, and an aqueous
solution having an adjusted pH of 4 and a temperature of 45°C were used, and a
cathode-electrolysis was performed under a current deusity of 55 A.ld111~th at exceeded
the critical current density, thereby forming aNi plating layer on the steel sheet. The
adhesion amount of Ni was controlled using the electrolysis time.
[0049]
[Ni plating condition 31
Anickel sulfate having a concentration of 20%, a nickel chloride having a
concentration of lo%, and an aqueous solution having at1 adjusted pH of 2 and a
temperature of 35°C were used, and a cathode-electrolysis was performed under a
current density of 10 A/dm2 that was lower than the critical current density, thereby
forming a Ni plating layer on the steel sheet. The adhesiotl atnount of Ni was
controlled using the electrolysis time.
[OOSO]
[Ni plating condition 41
A boric acid having a concentration of 3%, a nickel sulfate having a
concentration of lo%, a nickel chloride having a concentration of lo%, and an aqueous
solution having an adjusted pH of 4 and a temperature of 45°C were used, and a
cathode-electrolysis was perfonned under a current density of 20 Ndm2 that exceeded
the critical current density, thereby forming a Ni plating layer on the steel sheet. The
adhesion amount of Ni was controlled using the electrolysis time.
[0051]
[Treatment conditions of the chromate film layer]
A cathode-electrolysis was performed at 10 A/dm2 in an aqueous solution
including a chromium (Vr) oxide having a concentration of lo%, a solfi~rica cid having
a concentration of 0.2% and a11 ammonium fluoride having a concentration of 0. I%,
and water washing was perfonned for 10 seconds, thereby fonning a chromate film
layer on the Ni plating layer. The adhesion amount of Cr in the chromate film layer
was controlled using the electrolysis time.
[0052]
[Treatment conditions of the filrn layer including Zr]
A cathode-electrolysis was performed at 10 A/dm2 in an aqueous solution of a
zirconium fluoride having a concentration of 596, a phosphoric acid having a
concentration of 4% and a fluoric acid having a concentration of 5%, thereby forming
a film layer including Zr on the Ni plating layer. The adhesion amount of Zr in the
film layer including Zr was controlled using the electrolysis time.
[0053]
(2) Evaluation method of the specimens
(A) Weldability
First, the specimen (plating steel sheet) obtained using the above-described
method was used as a test specimen, a 15 pm-thick PET film was laminated on the test
specimen, arid welding was performed at changed currents under conditions of a lap
part of 0.5 rmn, a welding pressure of 45 kgf (1 kgf is equal to approxinlately 9.8 N.)
and a welding wire speed of 80 mlmin. The ranges of the appropriate welding
conditions were comprehensively determined from the width of an optimal current
range consisting of the ~ninimuncl urrent value at wvllich a sufficient weld strength
could be obtained and the maximum current value at which a welding defect such as
scatter began to appear, and the stabilized welding state, and the ranges were evaluated
into 4 levels (A: extremely wide, B: wide, C: no practical problem, D: narrow).
[0054]
(B) Adhesion
A 15 pm-thick PET film was laminated on the specimen obtained using the
above-described method, and a cup was produced through DrD pressing. The cup
was formed into a DI can using a DI machine. The exfoliation status of the film in
the can wall portion of the Dl can after the forming was observed, and was
comprehensively evaluated into 4 levels (A: exfoliatio~wl as not observed, B: slight
film floating was observed, C: significant exfoliation was observed, D: the film was
exfoliated during the DI forming, and tlie cylinder was broken).
[0055]
(C) Secondary adhesion
A 15 pm-thick PET fihn was laminated on the specimen obtained using tlie
above-described method, and a cup was produced through DrD pressing. The cup
was formed into a Dl can using a DI machine. After that, a thermal treatment was
performed at a temperature higher than t11e melting point of the PET film
(approximately 24OoC) for 10 minutes, and, filrthermore, the DI can was treated (retort
treatment) in a heated moisture atmosphere at 125'C for 30 minutes. In addition, the
exfoliation status of the film in the can wall portion of the DI can after tlie retort
treatment was observed, and was coinprellensively evaluated into 4 levels (A:
exfoliation was not observed, B: slight film floating was observed, C: significant
exfoliation was observed, D: the film was exfoliated during the DI forming, and the
cylinder was broken).
[0056]
(D) Corrosion resistance
A welded can on xv11ich a 15 pm-thick PET film was laminated was produced
using the specimen obtained using the above-described metl~od, and the welded portion
was coated with refinish paint. After that, a test liquid consisting of a liquid mixture
of 1.5% citric acid and 1.5% common salt was loaded into the welded can, a lid was
attached and sealed, and the can was stably left in a cot~sta~lt-temperatucrhea mber for
one month in an environment of 55°C. After that, the corrosion status in the damaged
film portion inside the welded can was determined and evaluated into 4 levels (A:
piercing corrosion was not observed, B: slight piercing corrosioil resulting in no
practical problem was obsetved, C: the progress of piercing corrosion was observed,
D: a hole was generated due to piercing corrosion).
[0057]
The evaluation results of the ~veldability,a dhesion, secondary adhesion and
corrosion resistance of Examples 1 to 11 and Comparative Examples 1 to 7 in which
the adhesion amonnt of the Ni plate, the concentration of an oxygen atom of the
hydroxyl Ni or the Ni oxide, and the chromate film layer or the film layer including Zr
was formed are described in Table 1. In Table 1, numeric values which are not within
the ranges of the invention are underlined.
[0058]
Meanwhile, in Table 1, the adhesion amount (dm2) of the Ni plate, and the
concentration (atomic%) of an oxygen aton1 of the hydroxyl Ni or tlie Ni oxide in tlie
Ni plating layer were specified by measuring the specitnens after Ni plating using an
X-ray photoelectron spectroscopy (XPS).
[OOS9]
[Table 11
[0060]
As described in Table 1, it is found that the steel sheets of Invention Examples
1 to 11 are all excellent in terms of weldability, adhesion, secondary adhesion and
corrosion resistance.
[0061]
In Comparative Example 1, since the adhesion amount of the Ni plating layer
was low, the weldability and tlie corrosion resistance particularly degraded.
[0062]
Comparative Exaniples 2 and 3 are examples in which the specimens were
produced under [Ni plating condition 331 and [Ni plating condition 41, and in which the
current densities were outside the range of the invention. In Comparative Examples 2
and 3, since tlie current densities were too low, the concentrations of oxygen atoms in
the Ni plating layer deviated from the range of the invention, and the corrosion
resistance degraded.
In Comparative Example 4, the concentration of an oxygen atom in the Ni
plating layer was outside the range of the invention, and the weldability degraded.
[0063]
In Comparative Exatnples S and 6, the adhesion amount of the chromate film
layer was outside the range of the invention, the secondary adhesion degraded in
Comparative Example 5, and the weldability degraded in Comparative Example 6,
respectively.
[0064]
In Comparative Examples 7 and 8, the adhesion amount of the film layer
including Zr was outside the range of the invention, the secondary adhesion degraded
in Comparative Example 7, and the weldability degraded in Comparative Example 8,
respectively.
[0065]
[Example 21
Next, a plurality of 0.2 mm-thick cold-rolled steel sheets for a tin plate with a
temper grade of 3 (T-3) was used as tin mill black plates, plating was performed under
each of the same Ni plating conditions as in "Example l", and a Ni plating layer was
fonned on each of the steel sheets. The adhesion amount of Ni wvas fixed to 0.7 &.
[0066]
Subsequently, a chromate film layer was formed on the Ni plating layer under
the same chromate treatment conditions as in "Exatnple 1". The adhesion amount of
Cr of the chromate film layer was fixed to 8 g/m2.
[0067]
The same (D) corrosion resistance test as in "Example 1" was perfonned on a
variety of the obtained plating steel sheets, and tlle depths of piercing corrosion were
measured. The obtained results are illustrated in FIG. 1. Meanwhile, "Condition I",
"Condition 3" and "Condition 4" described in FIG. 1 respectively refer to "Ni plating
condition I", "Ni plating condition 3" and "Ni plating condition 4".
In addition, for Invention Exarnple 1 described in Table 1, the concentration
(atomic%) of an oxygen atom of tbe hydroxyl Ni or the Ni oxide in the Ni plating layer
was measured using an X-ray photoelectron spectroscopy (XPS). The obtained
results are illustrated in FIG. 2.
[0068]
It is found that the piercing corrosion depth is 0.02 to 0.05 mnl at a
concentration of oxygen atoms of the hydroxyl Ni or the Ni oxide in the Ni plating
layer of 1 to 10 atomic% as illustrated in FIG. 1, and the corrosion resistance against
piercing corrosion significantly improves. At a concentration of oxygen atoms of 1 to
20 atomic%, corrosion proceeded along the interface behveen the Ni plating layer and
the base iron. On the other hand, at a cor~centrationo f oxygen atoms of less than 1
atomic%, corrosion proceeded along the thickness direction of the steel sheet.
[0069]
In addition, it is found that, in the steel sheet (Invention Example 1) including
the Ni plating layer manufactured using the manufacturing method that is within the
range of the invention, the concentration of an oxygen atom is 1 to 10 atomic% inside
the Ni plating layer as illustrated in FIG. 2. Meanwhile, the concentration of oxygen
atoms becomes high on the surface of the Ni plating layer (an area until the sputtering
time reached 10 minutes), and this is considered to be because the surface of the Ni
plating layer is oxidized and a natural oxide film is formed.
Meanwhile, the horizontal axis illustrated in FIG. 2 indicates the sputtering
time in XPS, but the time is equivalent to the depth ft0111 the surface of theNi plating
layer.
[0070]
Thus far, the preferred embodiment of the inventio~ha~s been described in
detail with reference to the accompanying drawings, but the invention is not limited to
such examples. It is evident that a person having ordinary skill in the technical field
of the invention can invent a variety of modification examples or correction examples
within the scope of the technical idea described in the claims, and it is natural to
consider those examples belonging to the technical scope of the invention.
. g- E=! Sss-gS
Z
00
Z -
Qs
WmaTa
Z
0
W
L n
- 4
E
='
2 -
&'
E
E -
z
P9&'
5
S12-g
0-
LL
INVENT I ON EXAMPLES COMPARATIVE EXAMPLES
a
I
c"
1
m
A'-'
a
m
I I
* m g r n =
1
I
u
m
a
m
I
a a a j 4 a a j 4 4 4 1 n n a r n < m a
j a a a 4 ~ a j a a a 1 a n a n 4 n a
a a a a 4 a a u a a a m a a a a a a a
a a a a u a a a a a < j a a o a n a n
d z g &
I
n
0
m
0
0
n
1
si;
-
I
1
I d "1 91
I
+o / I
I
1
bh0j qIl
[Document Type] CLAIMS
[Claim 11
A steel sheet used to manufacture a container, the see1 sheet comprising:
a Ni plating layer; and
a chromate film layer or a film layer including Zr, on the Ni plating layer,
wherein the Ni plating layer includes one or more of a hydroxyl Ni and a Ni
oxide,
an adhesion amount of the Ni plating layer in terms of an amount of Ni is 0.3
g/m2 or more,
a concentration of oxygen atorns of the Ni plating layer due to the hydroxyl Ni
and the Ni oxide is 1 to 10 atomic'30,
an adhesion amount of the cl~romatefi lm layer in terms of an a~nounot f Cr is
1 to 40 mg/m2, and
an adhesion amount of the film layer including Zr in terms of an amount of Zr
is I to 40 tng/m2.
[Claim 21
The steel sheet used to manufacture a container according to claim 1, wherein
the concentration of oxygen atoms is 1 to 10 atomic% in an entire area of a
thickness of the Ni plating layer excluding a natural oxide film formed on a surface of
the Ni plating layer.
[Claim 31
A method of manufacturing a steel sheet used to manufacture a container
according to claim 1, the method comprising:
forming the Ni plating layer including one or more of the hydroxyl Ni and the
Ni oxide by dipping a base steel sheet in a plating bath and then performing a cathodeelectrolysis
under a current density higher than a critical current density of
precipitatioti of Ni, wherein the plating bath consist's of an aqueous solution in wliicll
one or more of a Ni sulfate and a Ni chloride is dissolved, and
fonning the chromate film layer of whicli tlie adhesion amount in terms of the
amount of Cr is 1 to 40 rng/m2 on the Ni plating layer or fortnirig the film layer
including Zr of \vlvhich tlie adhesion amount in tenns of tlie amount of Zr is 1 to 40
mg/d, on the Ni plating layer.